Emissions and Dynamics: The Role of Software in Similar Automotive Platforms ^†

Abstract

The development of internal combustion engines aims to maximize the combustion process energy, achieve the highest possible efficiency, and reduce harmful emissions released into the environment, while also improving power output. In this regard, here we have presented two pairs of vehicles which have mechanically similar internal combustion engines but either different environmental or dynamic performance characteristics. The first example is of upgrading an internal combustion engine from Euro 4 to Euro 5. The second example demonstrates a 23% increase in power while maintaining the same emission parameters.

1. Introduction

From the days of the Second Industrial Revolution to the present, the design of the main components of the internal combustion engine and its basic operating principles have been retained. In regard to future developments, the aim is to reduce exhaust emissions and bring vehicles into a higher environmental category [1]. This obstacle reflects on the whole environmental surrounding, and on the people in public areas [2]. This includes quantitative studies of key environmental indicators of vehicles in service. Such improvements could be achieved by optimizing the parameters characterizing the operation of automotive electronic systems, without the need for investment in mechanical modifications. Undoubtedly, automakers strive to maximize the potential of the current generation of engines before starting the development of a completely new powertrain [3]. This is necessary not only from a practical standpoint, but also due to the substantial financial and time costs involved in creating a new engine that will ultimately be installed in mass-produced vehicles.

2. Materials and Methods

The focus is on optimizing compression-ignition internal combustion engines from the main target group, namely Euro 4 and Euro 5. The reason for this selection stems from the availability of modern auxiliary systems designed to improve the efficiency of the combustion process in internal combustion engines [4,5,6,7]. Engines in the Euro 0, 1, 2, and 3 are not as suitable for the purpose of this study. This is because for engines in the Euro 0 and Euro 1 groups, the control of processes in the internal combustion engine is either fully mechanical or performed by an electronic control unit, the modification of which requires significantly greater financial and time resources [8]. An additional factor is that such vehicles constitute a negligible percentage of the total fleet of passenger cars in operation within the territory of the Republic of Bulgaria [9]. Regarding passenger cars falling into the Euro 2 and Euro 3 groups, such optimization would be more feasible for them, given the types of ECUs and the possibility of optimizing the tables defining the parameters for controlling processes in the internal combustion engine. There is another problem that hinders the reduction in harmful exhaust emissions for these types of engines [10,11]. Internal combustion engines falling into these categories are not fully equipped with the necessary auxiliary systems to neutralize all toxic combustion byproducts.

While focusing on the Euro 4 and Euro 5 groups, a study was also conducted regarding the possibilities for modifying parameters in the ECU. Currently, there are several such products on the market that offer these modification capabilities. Using the funds provided by the project to support doctoral students, the Technical University of Sofia purchased the following equipment: a device for extracting files from the internal combustion engine control unit, KESS3 [12] (Figure 1).

This device, together with its appropriate software—ECM Titanium (Figure 2)—enables the retrieval of predefined control parameter values for the various modes of internal combustion engines. Both products sourced from Alientech S.r.l, Trino, Italy. This can be done for most makes and models of electronic control units, with few exceptions. The methods for extraction are categorized into three main types: via the on-board diagnostic system, by connecting the device to the corresponding ECU terminals, or by connecting directly to the chipset that contains this information [13,14]. After extraction of the file, the ECM Titanium is required to perform any necessary modification of one or more parameters. After ensuring the ability to work with these devices, we proceeded to create a database of the examined environmental indicators of internal combustion engines. By extracting such information from numerous vehicles, we managed to identify several key strategies adopted by most automakers. The first of these strategies is the limitation of the maximum values of the parameters that control the processes in the ICE [15]. These are precisely the maximum permissible values, beyond which the probability of failure of any of the components or entry into the zone of excessive wear due to operation is deliberately reduced [16]. There are several reasons for these limitations: the use of partial potential to extend the service life of the unit; compliance with a specific environmental group; compliance with a specific power range; and others. This study focused on two main areas. Study of the software control strategy aimed at achieving performance indicators that allow classification into a specific environmental group and a specific power range [17,18,19,20]. For the purpose of this experiment, two pairs of vehicles were selected, equipped with engines of identical mechanical design but with different output parameters.

2.1. Different Power Output—Same Emission Standards

In this category, the study focuses on two Skoda Rapid (NH3) passenger cars equipped with engines featuring spark ignition, turbocharging, and direct fuel injection, which meets Euro 6 emission standard. The study shows that the upgrade of the CJZC engine to the CJZD engine was not intended to meet higher environmental standards, but rather to achieve a higher power range; see

Table 1. CJZC and CJZD technical specifications.

Engine Type	VAG EA211 Inline-Four Petrol Engines CJZC	VAG EA211 Inline-Four Petrol Engines CJZD
Design & principle	Four-cylinder in-line engine, four-stroke Otto cycle, turbocharged, gasoline direct injection	Four-cylinder in-line engine, four-stroke Otto cycle, turbocharged, gasoline direct injection
	1197 cm3	1197 cm3
	66 kW (90 hp)/4400–5400 rpm	81 kW (110 hp)/4600–5600 rpm
Max. torque at speed	160 Nm/1400–3500 rpm	175 Nm/1400–4000 rpm
	10.5:1	10.5:1
Max. engine speed	6300 rpm	6300 rpm
	Dual overhead camshaft with variable valve timing	Dual overhead camshaft with variable valve timing
Camshaft drive	Timing belt	Timing belt
	71 mm	71 mm
Piston stroke	75.6 mm	75.6 mm
Intake manifold	Plastic inlet manifold and charge air cooler	Plastic inlet manifold and charge air cooler
	BOSCH MED17.5.5	BOSCH MED17.5.5
	Unleaded petrol, min. 95 ROZ	Unleaded petrol, min. 95 ROZ
Exhaust after treatment	Three-way catalytic converter with one step-type Lambda probe before and one after the catalytic converter which is positioned directly behind the turbocharger in an L shape to minimize space and achieve maximum temperature rapidly. Underbody Catalyst: A second three-way catalytic converter located under the vehicle to ensure compliance with emissions standards under heavy loads.	Three-way catalytic converter with one step-type Lambda probe before and one after the catalytic converter which is positioned directly behind the turbocharger in an L shape to minimize space and achieve maximum temperature rapidly. Underbody Catalyst: A second three-way catalytic converter located under the vehicle to ensure compliance with emissions standards under heavy loads.
	Euro 5B	Euro 5B
Lubrication system	Oil pressure; engine oil cooler; piston crown spray cooling	Oil pressure; engine oil cooler; piston crown spray cooling
	Liquid, dual-circuit cooling system, electronically controlled	Liquid, dual-circuit cooling system, electronically controlled
Ignition system	Ignition coil on spark plug; high-energy ignition; cylinder-selective knock detection	Ignition coil on spark plug; high-energy ignition; cylinder-selective knock detection

. From here, the next step in the process is to extract the files from the two vehicles. This is followed by a detailed analysis, revealing the presence of 132 control maps for the CJZC engine and 122 for the CJZD engine; see Figure 3.

A more detailed analysis of the additional control parameters reveals that they do not directly affect the transition from CJZC to CJZD. These parameters are only applied under operating conditions that deviate from normal operation, such as limp mode, cold start, idle running, etc. This shifts the focus to the remaining parameters [21]. The only parameter that is found to directly affect the vehicle’s dynamic performance and limits the engine’s torque, and consequently its power, is the limiter of maximum torque (%). This indicates that the software is designed so that, when the driver applies full throttle, the engine does not deliver its absolute power potential, but rather the highest potential within the range before irreversible mechanical changes occur in the components [22]. As a result of this torque limitation across the entire frequency range, a curve is formed that determines the maximum torque and, consequently, the maximum power; see

Table 2. CJZC—torque limit, %.

Limiter of Maximum Torque, CJZC, 66 kW
RPM	%
1000	28.11
1250	47.55
1400	46.50
1500	46.76
2000	47.00
2250	45.82
2520	45.17
3000	44.99
3520	45.58
4000	44.36
4520	40.80
4800	38.98
5000	38.00
5500	34.50
6000	31.87
6300	29.29

and

Table 3. CJZD—torque limit, %.

Limiter of Maximum Torque, CJZD, 81 kW
RPM	%
1000	28.11
1250	48.36
1400	51.2
1500	50.31
2000	50.2
2250	49.78
2520	50.19
3000	50.1
3520	50.29
4000	50.37
4520	50.41
4800	45.34
5000	41.73
5500	39.68
6000	37.88
6300	35.71

and Figure 4. To allow for changes in torque limits, the remaining tables defining the air–fuel ratio, supercharging, ignition timing, etc., are designed to ensure proper operation of the internal combustion engine, even at power levels exceeding those set by the limits.

2.2. Same Power Output—Different Emission Standards

In this segment, the study focuses on two Opel Astra H passenger cars. The first one is an Opel Astra H equipped with an internal combustion engine (ICE) with the manufacturer’s code Z18XER. The second car is identical but equipped with an ICE A18XER. The technical specifications of the two engines are listed in

Table 4. Technical specification—Z18XER, A18XER.

Engine Type	General Motors 1.8L I-4 Fam1 Gen3 Z18XER	General Motors 1.8L I-4 Fam1 Gen3 A18XER
Design & principle	Four-cylinder in-line engine, four-stroke Otto engine	Four-cylinder in-line engine, four-stroke Otto engine
	1796 cm3	1796 cm3
	103 kW (140 hp) at 6300 rpm	103 kW (140 hp) at 6300 rpm
Max. torque at speed	175 Nm at 3800 rpm	175 Nm at 3800 rpm
	10.5:1	10.5:1
Max. engine speed	6500 rpm	6500 rpm
	2 top-mounted, double continuous phase-adjustable (DCVCP)	2 top-mounted, double continuous phase-adjustable (DCVCP)
Camshaft drive	Timing belt	Timing belt
	80.5 mm	80.5 mm
Piston stroke	88.2 mm	88.2 mm
Intake manifold	Plastic, two-stage suction length adjustment	Plastic, two-stage suction length adjustment
	Siemens Simtec 75.1	AcDelco E83
	91/95/98 RON	91/95/98 RON
Exhaust aftertreatment	Close-coupled 3-way catalytic converter with 2 lambda sensors	Close-coupled 3-way catalytic converter with 2 lambda sensors
	Euro 4	Euro 5
Lubrication system	Oil pressure; engine oil cooler; piston crown spray cooling	Oil pressure; engine oil cooler; piston crown spray cooling
	Liquid, closed circuit; electronically controlled	Liquid, closed circuit; electronically controlled
Ignition system	Ignition coil on spark plug; high-energy ignition; cylinder-selective knock detection	Ignition coil on spark plug; high-energy ignition; cylinder-selective knock detection

. After inspection of the mechanical structure of the engines, it was determined that the difference in emission category, Euro 4 and Euro 5 [23,24] (

Table 5. European standards—Euro 4 and Euro 5—characterizing values.

Parameter	Euro 4 (Petrol)	Euro 5 (Petrol)
Relevant EU Directives/Regulations	Directive 98/69/EC [23] & Directive 2002/80/EC [25]—set Euro 4 emission limits (for cars and light vans)	Regulation (EC) No 715/2007 [24] together with Regulation (EC) No 692/2008 [26]—set Euro 5 emission limits (and later amendments)
Date of Introduction—Type Approval	1 January 2005 (new type approvals)	1 September 2009 (new type approvals)
Date of Introduction—All New Registrations	1 January 2006	1 January 2011 (typical timing after approval)
CO (Carbon Monoxide)	1.0 g/km	1.0 g/km
HC (Unburned Hydrocarbons)	0.10 g/km	0.10 g/km
NOx (Nitrogen Oxides)	0.08 g/km	0.06 g/km
PM (Particulate Matter)	Not regulated for port injection	0.005 g/km only applicable to direct-injection petrol (not applicable to port-injected engines)
PN (Particle Number)	Not regulated	6.0 × 1011 #/km only for direct-injection petrol under Euro 5b (no limit for port injection)

), comes solely from the electronic control units that manage the processes in the internal combustion engines. As a result of this the emissions category to which the engines belong are different. see Figure 5.

The difference in the type of control units lies in the refinement of the control by using a larger number of points that describe the operating functions of the internal combustion engine systems. In the first case, I present a three-dimensional graph that determines the variable gas distribution of the intake valves. This in itself is a key factor in determining the volumetric efficiency of the internal combustion engine [27,28,29]; see Figure 6 and Figure 7.

The 3D graphics determine the spark advance angles. Based on data in a Siemens ECU, the map has been defined by 192 parameters, whereas in AcDelco ECU the parameter which defines the map is 561; see Figure 8 and Figure 9.

3. Results

After analyzing the conducted studies, the output data on the composition of the exhaust gases was collected. The measurements are performed using the gas analyzer, which determines the amount of five of the main components: CO₂, CO, HC, O₂, and NOx. Despite the extensive analysis, it is not possible to use the obtained results directly for optimization purposes, since their quantitative determination is defined in units of measurement different from that generally accepted for use in the European categorization of passenger cars, namely grams per kilometer (g/km). The device that was used measures the content of emissions in the exhaust gases in percentages for CO, CO₂, and O₂, respectively. The content of HC and NOx is measured in ppm Vol. This is a unit of measurement for volumetric concentration, which determines parts per million per unit volume. The difference in the two types of measurements, quantitative and volumetric, is an obstacle to the calculation, but not to the comparison of the two cars from each pair. For the purpose of the comparison, the idling mode was chosen.

Table 6. Exhaust emissions components comparison.

Engine Type	Eng.Sped	Oil Temp	CO2	HC	Nox	λ	O2	CO	Exhaust Gas
	rpm	°C	%	ppm Vol	ppm Vol	-	%	%	deg C
Z18XER	802	80	14.40	37	5	1.020	0.61	0.09	42
A18XER	800	81	14.60	26	5	1.020	0.59	0.06	42
CJZC	750	75	14.70	28	3	0.990	0.00	0.08	42
CJZD	750	73	14.70	27	3	0.990	0.00	0.08	41

presents the measurement data.

4. Conclusions

Improvements made to the environmental efficiency do not always have a negative impact on the performance of internal combustion engines. The examples presented above clearly show that, on the one hand, more precise control and, on the other, equipping the engine with the necessary additional systems can lead to remarkable dynamic performance combined with high environmental efficiency as well as a long service life. The direction in which more scientific effort should be invested is precisely the optimization of the operation of previous-generation internal combustion engines. The aim should be to reduce the harmful combustion byproducts they emit into the atmosphere until the end of their service life. This additional contribution will make it possible to achieve the service life specified by the manufacturer while reducing the harmful emissions released by the vehicle. In this way, the generation of an incredibly large amount of emissions is prevented, facilitating the recycling of currently existing vehicles, as well as a more rational transition to the next generation of motor vehicles.